Process for treating hydrocarbon oils



Patented Nov. 12, 1935 UNITED- STATES PROCESS FOR TREATING HYDROCARBON OILS Walter A. Sohulze and Lovell V. Chaney, Battles ville, kla., assig'nors to Phillips Petroleum Company, Bartlesville, Okla a corporation of Delaware No Drawing. Application June 20. 1933, Serial No. 678,782

Claims. (Cl. 193-24) This invention relates to improvements in the method of treating hydrocarbons and the like with alkali polysulfldes and/or certain alkaline earth polysulfides. In particular, it relates to the removal of elementary sulfur from petroleum and coal tar hydrocarbon liquids and similar substances by means of sodium, potassium and ammonium polysulfides.

It has for its primary purpose the removal of elementary sulfur from petroleum and naphthas, natural gasolines, petroleum hydrocarbons fractions and other petroleum oils, benzol, solvent naphtha, and other coal tar products, and from other sulfur-containing solvents responding to such treatment.

The presence of elementary sulfur in motor fuels and other petroleum products is objectionable on account of the tendency of elementary, or free, sulfur to react with certain metals, particularly at elevated temperatures, and to produce other corrosive substances when burned in internal combustion engines. Recognition of this tendency is at present exemplified by the rigid specifications included in the U. S. motor gasoline specifications (U. S. Bureau of Mines Technical Paper 323 '13), wherein the requirements for passing the so-called corrosion test specify no discoloration of a clean copper strip after three hours submersion in the fuel under test at a temperature of 50 C. (122 F.). This test is sensitive to approximately 0.005 per cent elementary sulfur in the material tested.

The method of treatment described in the present invention removes elementary sulfur from such types of motor fuels, and many other sulfur-containing solvents, to the extent that they will respond negatively not only to the above-mentioned corrosion test, but also to a test sensitive to 0.00004 per cent of elementary sulfur.

The ability of alkali mono-sulfides to combine with elementary sulfur to form polysulfldes is well known, as may be found in almost any inorganic chemistry text-book. Mellor, for instance, very ably discusses this subject in his Inorganic and Theoretical Chemistry vol. II, p. 629 et seq., Longmans, Green and Company, 1927.

Sodium mono-sulfide, (Nels), has been used for removing elementary sulfur from various solvents therefor, usually at more or less elevated temperatures. Potassium mono-sulfide accomplishes this result much more readily than does sodium mono-sulfide, and at lower temperatures. At present, the latter method is l'iandicapped commercially due to cost factors.

Cobb (U. S. Patents 1,300,816 and 1,413,005) uses alkali and alkaline earth mono-sulfides to remove sulfur from petroleum hydrocarbons at temperatures from 160 to 190 F. He may also use alkali and alkaline earth hydroxides to accomplish his purpose where the material being treated also contains hydrogen sulfide, again working at quite elevated temperatures.

Alkali polysulfides have heretofore never been utilized in treating liquids of the character hereinbeforeenumerated in such a manner as to make the method commercially practicable; that is, no disclosure has'heretofore been made of a rapid and inexpensive method for quickly. and completely removing dissolved elementary sulfur from sulfur-containing solvents at ordinary atmospheric temperatures. By ordinary atmospheric temperatures are meant temperatures between approximately 40 and 90 F. We have succeeded in accomplishing these results with alkaline polysulflde solutions, the substantiating data and preferred methods of operating being hereinafter set forth.

y We have determined that sodium polysulfides,

as typical of the allrall polysuifides, rapidly and i completely remove elementary sulfur from hydrocarbon solvents at ordinary atmospheric temperatures (40 to 90 F.) when the composition of the polysulflde is approximately between NazSm and Naesl, the most rapid removal 00- curring with sodium polysulfides whose compositions are approximately represented by NazSz and Nazsz, and those of intermediate sulfur content. Sodium polysulfldes with smaller amounts of sulfur in combination than represented by NaaS1.1 also remove elementary sulfur quantitatively but somewhat more slowly, the time and extent of agitation or contacting for complete sulfur removal becoming considerably greater as the composition of the polysulfide approaches NazS, where the sulfur is not completely removed even though contacted as much as to times as long as with similar concentrations of Nazszs or NazSa, for instance, which completely remove the sulfur. 60

petroleum hydrocarbon fraction composed principally of heptanes, the following are cited:

ing the desulfurlzing eflectiveness of the solution. An atmosphere of air oxidizes the polysulfldes quite rapidly, and while it is not absolutely necessary to prevent access of air or other oxidizing substance to the solutions, it is advantageous 1 salmon Elementary P 1 d 1 a i i t 1 r 'filllllle'gg 352:

1'0 cum I0 111 [8C- o-yqum on V0lumes0i30 Volumes of ira iontroated tio treatod gg zg 10 p0 Be. NaOH of H10 per cent BIB-[I8 A (N818) (Mono-snlfldeior comparison) (1. 0) (0.0) (4.0) (00 (0.001 (Incomplotely removed in 16 1 50 minutes.) 1.0 00 4.0 00 0.001 zommuoos. 0.15 0.0 4.25 00 0.001 12 minutes 1.0 a0 4.0 00 0.001 l05seconds 1.0 6.0 4.0 00 01!)? 42oeconds 1.0 5.0 4.0 ill 0.007 30seoonds 3.0 so 20 00 0.001 34seoonds. 3.0 5.0 2.0 ill 0.007 l3seconds 3.0 0.0 20 00 0.001 iosooooos 3.0- 0.0 2.0 00 0.001 usoooods. 3.0 6.0 2.0 00 0.007 38sooonds.

0.0 so 00 0.001 absooooos. 5.0 6.0 ii) 0.143 85seconds. goo? 0.0V 00 0.143 ossoooods. 5.0 5.0 00 0.143 iosoconds. 5.0 5.0 00 0.143 28seoonds. 5.0 5.0 00 0.007 Zlsooonds. I 5.0 an 00 0.001 10 seconds. grog 0.0 00 0.001 Gseoonds. 30 5.0 6.0 60 0.007 8seconds.

5.0 .20 00 0.001 aosoooods. 4.0 a0 00 0.001 l8scoonds. 5.0 20 00 0.001 10 seconds. a0 2.0 00 0.001 12seeonds. 5.0 2.0 00 0.007 35seo0nds.

' 1.0 2.0 7 0 60 0.007 itllsoconds.

10 20 10 00 0.001 nosooondss 1.0 2.0 10 00 0.001 65seconds.

' 40 a0) (a0) 0004) IOminutes. 1.0 1.0 00 e001 eosooonds. 3.0 1.0 00 0.001 30seoonds. 1.5 8.5 00 0.007 15 seconds. 3.0 7.0 00 0.007 Sseconds.

1 All polysulfide solutions prepared by adding the required amount 0! elementary sulfur lot a given polysulphide to a sodium mono-' sulphide solution containing 145 g. oi N835 per liter.

The amount of sulfur in the solvent therefor that such oxidizing agents be absent or at a may vary considerablywithout appreciably alminimum, part y during agitation of h tering the speed of its removal with polysulfide treating agents with the sulfur-containing 501- solutions. vents, for the efiectlveness and longevity of the While the concentration of Nazis in the sodium treating agent is thereby greatly increasedmonosulfide base solution from which the poly- The P e of a Substantial e s 01 a asulfides are prepared may vary over a wide range linity is also desirable and preferable in the without materially affecting the activity of the treating solution. ugh this is not necessary resulting polysulflde treating solution; it is prefor the method to be operable. We obtain this ferred to use a base solution with about the same alkalinity wit somewhflt trated alkali NazS concentration as employed in preparing hydroxide, an'apploximately Sodium ythe polysulflde solutions used in obtaining the droxide s lu i n h vin n mp y s-- data shown in the above table. This basesolufully for this purpose in our method. A.pre-

tion was prepared by dissolving NazSBHQO in a minimum amount of water and the solution adjusted by dilution so that each liter of solution contained 145 g. of NazS. The concentration of NazS in the base solution may be increased up to 200 g. per liter, or the solution may beemployed with NaaS concentrations of the order of 50 to g. per liter.

Weighed amounts of elementary sulfur are added to'the sodium sulfide solution to produce the polysulflde desired. with occasional agitation, the sulfur readily dissolves in the sodium sulfide solution at atmospheric temperature. Raising the temperature of the polysulflde solutions is avoided due to rapid conversion of the polysulfides to thiosulfate, or otherwise destroyferred concentration of excess alkalinity is of the order of 150 g. of NaOH per liter, although the method is operable with little or no added alkallnity,. that furnished by NazCO: suflicing, or with quite high concentrations of NaOH; for example, 300 to 500 g. per liter. 65 It is desirable to work with treating solutions iairly concentrated in polysulfldes. While we prefer to operate with treating solutions containing about g. per liter oi NazSu, g. per liter of N328: or g. per liter of P683, as ex- 70 amples, the method accomplishes very good results with concentrations varying, for instance, from 15-20 g. per liter oi NazSLs to 200250 g. per liter; and from 20-30 g..per liter of No.18:

to 250-300 g. per, liter. 75

It is advantageous to conduct the treating operation at atmospheric temperatures, which may be taken as 40 to 90 F. Temperatures as low as 32 F. and-as high as 130-140 F. may be employed, but such high temperatures should be avoided, if possible, due to the tendency of the polysulfldes to lose their desulfurizing qualities at these elevated temperatures. Should the material to be treated have a temperature in the range of 100 to 140 F. when it arrives at the polysulfide treating stage, we prefer to let the material cool to,- or artificially bring the temperature to, at least 80 or 90 F. before treating with the polysulflde solution.

During the preparation and storage of the polysulflde solutions, the temperature of the solutions is kept well below 90 F., artificial cooling being resorted to when necessary.

- It is highly desirable, and we prefer, to treat with these polysufide solutions iii-the absence of air or other oxidizing agent, or in the presence of a minimum amount of thorn. An atmosphere of inert or non-oxidizing gas may be provided during the operation of the treating process, and

during preparation and storage of the polysul fide solutions.

In treating natural gasoline, refinery gasoline, petroleum hydrocarbon fractions, coal tar distillates or other elementary sulfur-containing solvent responsive to our desulfurizing method, one preferred mode of operation is to very intimately contact the material containing the dissolved sulfur with the polysulfide solution, the contacting being accomplished by any of the well known means and may be either batch or continuous. The more intimate the mixing or contacting, the more quickly and completely will the treating agent perform the sulfur removal. Following the contacting, the treating agent is separated from the material treated by settling and decantation.

By way of illustration, 9. treating solution containing NaaSz is prepared by dissolving a commercial grade of sodium sulfide in a minimum amount of water, adjusting the solution (from analysis or calculation) to an approximate concentration of 150 g. of NazS per liter (1.25 lb. per gallon) and adding 60 g; of elementary sulfur per liter (0.5 lb. per gallon); and agitating gently at 40 to F., with a minimum or no access of air, to' effect solution of the sulfur. The resulting polysulflde will have a composition approximating the disulfide, NaaSz. proximately an equal volume of 30 B. sodium hydroxide is mixed with the resulting solution, observing the same moderate temperatures and non-oxidizing atmosphere, and the treating solution is ready to remove elementary sulfur from hydrocarbon oils and the like. The substances comprising this treating solution will be present in approximately thefollowing concentrations:

NaaSz, 106 g. per liter NaOH, g. per liter For a treating solution prepared in a similar manner, but containing sufficient sulfur to form the polysulfide NazSa, the concentrations of the comprising substances would be approximately:

NuaSa, 137 g. per liter NaOH, 150 g. per liter tive efficiencies as desulfurizing means are shown by the following tabulation:

Time for complete sul- Polysulilde treating solution, 10 volumes volumes solvent containing 0.143 percent sulfur N815; (NaOH) 28 seconds. K18] (KOH) 60 seconds. (Mums, (Nmom 60 seconds. 10

1 Over 99 percent removed.

' Cami- )2 arid/or Ba OH z completely removing the elementary sulfur from hydrocarbon liquids 25 in 2 to 4 minutes. In the presence of solid Mg(OH)z, magnesium polysulfides remove alementary sulfur but do so quite incompletely.

Certain substances occurring in some gasolines tend to retard the above described desulphurizing action of alkaline polys'uifides. Some oxygenated bodies, such as unsaturated aldehydes, for instance, possess this retarding tendency, and while the complete removal of elementary sulfur from a given solvent for the sulfur is retarded, considerably in some cases, it is by no means impossible to extract the sulfur with the polysulfldes. A longer contacting period suffices to accomplish the removal. Furthermore, the retarding effect of such oxygenated bodies may often be lessened by contacting the sulfur-containing oil prior to the polysulfide treatment with a solution of a caustic alkali which may or may not contain a suitable reducing agent such as sodium stannite or the like.

From the foregoing it is believed that the steps and advantages of the process may be readily understood by those skilled in the art, and it is manifest that changes may be made in the details disclosed, without departing from the spirit of the invention, as expressed in the claims.

What is claimed and desired to be secured by Letters Patent is:

1. The process for removing elementary sulfur from petroleum oils, which comprises as the initial step, contacting the oil containing elementary sulfur at atmospheric temperature with an aqueous solution of a polysulfide lower than the tetrasulflde selected from the group consisting of the alkali and alkaline earth polysulfides, and separating the oil from the treating solution.

2. The process for removing elementary sulfur from petroleum oils, which comprises as the initial step, contacting the oil containing elementary sulfur at substantially atmospheric temperature with an aqueous solution of sodium polysulfldes lower than the sodium tetrasulfide', and separating the oil from the treating solution.

3. The process for removing elementary sulfur from petroleum oils, which consists of briefly con- 70 tacting the oil containing elementary sulfur at substantially atmospheric temperature with an aqueous solution of sodium disulfide, and separating the oil. from the treating solution.

4. In the process for removing elementary 5111- 75 fur removal from 60 5 fur from petroleum oils the step which consists in initially contacting the oil containing elementary sulfur at substantially atmospheric temperature with an aqueous solution consisting of sodium hydroxide and a sodium polysulfide lower than the tetrasulflde, and separating the oil iromthe treating solution.

5. The process-for removing elementary suli'ur from petroleum oils which comprises as the initial step contacting the oil containing elementary suifur at substantially atmospheric temperature with an aqueous solution of sodium polysulflde of the formula NazSx in which a: isnot less than 1.1 or

greater than 4, and separating the oil from the 5 treating solution.

WALTER A. SCHULZE. LOVELL V. CHANEY. 

